Achieving ideal transistor characteristics in conjugated polymer semiconductors

Molecular Ordering Manipulation in Fused Oligomeric Mixed Conductors for High-Performance n-Type Organic Electrochemical Transistors

Advanced n-type organic electrochemical transistors (OECTs) play an important part in bioelectronics, facilitating the booming of complementary circuits-based biosensors. This necessitates the utilization of both n-type and p-type organic mixed ionic-electronic conductors (OMIECs) exhibiting a balanced performance. However, the observed subpar electron charge transport ability in most n-type OMIECs presents a significant challenge to the overall functionality of the circuits. In response to this issue, we achieve high-performance OMIECs by leveraging a series of fused electron-deficient monodisperse oligomers with mixed alkyl and glycol chains. Through molecular ordering manipulation by optimizing of their alkyl side chains, we attained a record-breaking OECT electron mobility of 0.62 cm2/(V s) and μC* of 63.2 F/(cm V s) for bgTNR-3DT with symmetrical alkyl chains. Notably, the bgTNR-3DT film also exhibits the highest structural ordering, smallest energetic disorder, and the lowest trap density among the series, potentially explaining its ideal charge transport property. Additionally, we demonstrate an organic inverter incorporating bgTNR-3DT OECTs with a gain above 30, showcasing the material's potential for constructing organic circuits. Our findings underscore the indispensable role of alkyl chain optimization in the evolution of prospective high performance OMIECs for constructing advanced organic complementary circuits.

Modulation between capacitor and conductor for a redox-active 2D bis(terpyridine)cobalt(II) nanosheet via anion-exchange

Ionic polymers are intriguing materials whose functionality arises from the synergy between ionic polymer backbones and counterions. A key method for enhancing their functionality is the post-synthetic ion-exchange reaction, which is instrumental in improving the chemical and physical properties of polymer backbones and introducing of the functionalities of the counterions. Electronic interaction between host polymer backbone and guest ions plays pivotal roles in property modulation. The current study highlights the modulation of responses to external electric field in cationic bis(terpyridine)cobalt(II) polymer nanofilms through anion-exchange reactions. Initially, as-prepared chloride-containing polymers exhibited supercapacitor behaviour. Introducing anionic metalladithiolenes into the polymers altered the behaviour to either conductive or insulative, depending on the valence of the metalladithiolenes. This modulation was accomplished by fine tuning of charge-transfer interactions between the bis(terpyridine)cobalt(II) complex moieties and redox-active anions. Our findings open up new avenue for ionic polymers, showcasing their potential as versatile platform in materials science.

A Three-in-One Hybrid Strategy for High-Performance Semiconducting Polymers Processed from Anisole

The development of semiconducting polymers with good processability in green solvents and competitive electrical performance is essential for realizing sustainable large-scale manufacturing and commercialization of organic electronics. A major obstacle is the processability-performance dichotomy that is dictated by the lack of ideal building blocks with balanced polarity, solubility, electronic structures, and molecular conformation. Herein, through the integration of donor, quinoid and acceptor units, an unprecedented building block, namely TQBT, is introduced for constructing a serial of conjugated polymers. The TQBT, distinct in non-symmetric structure and high dipole moment, imparts enhanced solubility in anisole-a green solvent-to the polymer TQBT-T. Furthermore, PTQBT-T possess a highly rigid and planar backbone owing to the nearly coplanar geometry and quinoidal nature of TQBT, resulting in strong aggregation in solution and localized aggregates in film. Remarkably, PTQBT-T films spuncast from anisole exhibit a hole mobility of 2.30 cm2 V-1 s-1, which is record high for green solvent-processable semiconducting polymers via spin-coating, together with commendable operational and storage stability. The hybrid building block emerges as a pioneering electroactive unit, shedding light on future design strategies in high-performance semiconducting polymers compatible with green processing and marking a significant stride towards ecofriendly organic electronics.

Constructing N-Containing Poly(p-Phenylene) (PPP) Films Through A Cathodic-Dehalogenation Polymerization Method

Developing the films of N-containing unsubstituted poly(p-phenylene) (PPP) films for diverse applications is significant and highly desirable because the replacement of sp2 C atoms with sp2 N atoms will bring novel properties to the as-prepared polymers. In this research, an electrochemical-dehalogenation polymerization strategy is employed to construct two N-containing PPP films under constant potentials, where 2,5-diiodopyridine (DIPy) and 2,5-dibromopyrazine (DBPz) are used as starting agents. The corresponding polymers are named CityU-23 (for polypyridine) and CityU-24 (for polypyrazine). Moreover, it is found that both polymers can form films in situ on different conductive substrates (i.e., silicon, gold, ITO, and nickel), satisfying potential device fabrication. Furthermore, the as-obtained thin films of CityU-23 and CityU-24 exhibit good performance of alkaline hydrogen evolution reaction with the overpotential of 212.8 and 180.7 mV and the Tafel slope of 157.0 and 122.4 mV dec-1, respectively.

Achieving Ideal and Environmentally Stable n-Type Charge Transport in Polymer Field-Effect Transistors

Realizing ideal charge transport in field-effect transistors (FETs) of conjugated polymers is crucial for evaluating device performance, such as carrier mobility and practical applications of conjugated polymers. However, the current FETs using conjugated polymers as the active layers generally show certain non-ideal transport characteristics and poor stability. Here, ideal charge transport of n-type polymer FETs is achieved on flexible polyimide substrates by using an organic-inorganic hybrid double-layer dielectric. Deposited conjugated polymer films show highly ordered structures and low disorder, which are supported by grazing-incidence wide-angle X-ray scattering, near-edge X-ray absorption fine structure, and molecular dynamics simulations. Furthermore, the organic-inorganic hybrid double-layer dielectric provides low interfacial defects, leading to excellent charge transport in FETs with high electron mobility (1.49 ± 0.46 cm2 V-1 s-1) and ideal reliability factors (102 ± 7%). Fabricated polymer FETs show a self-encapsulation effect, resulting in high stability of the FET charge transport. The polymer FETs still work with high mobility above 1 cm2 V-1 s-1 after storage in air for more than 300 days. Compared with state-of-the-art conjugated polymer FETs, this work simultaneously achieves ideal charge transport and environmental stability in n-type polymer FETs, facilitating rapid device optimization of high-performance polymer electronics.

Aldol Condensation for the Construction of Organic Functional Materials

Aldol condensation is a cost-effective and sustainable synthetic method, offering the advantages of low complexity, substrate universality, and high efficiency. Over the past decade, it has become popular for creating next-generation organic functional materials, particularly rigid-rod conjugated (semi)conductors. This review focuses on conjugated small molecules, oligomers, and polymeric (semi)conductors synthesized through aldol condensation, with emphasis on their remarkable features in advancing n-type organic field-effect transistors (OFETs), organic electrochemical transistors (OECTs), organic photovoltaics (OPVs), and organic thermoelectrics (OTEs) as well as NIR-II photothermal conversion. Coherence character, optical properties, microstructure, and chain conformation are investigated to understand material-property relationships. Future applications and challenges in this area are also discussed.